Angus Mengsk believed that the Terran Confederacy and the Old Families were corrupt. His views had become quite popular amongst the people of Korhal IV and his oratorical skills swayed many senators to his cause. However, his son, Arcturus, didn't agree with these views. The two didn't get along in many areas, with Arcturus believing Angus was trying to control his life. Arcturus wanted to become a prospector, which Angus strongly disapproved of.[1]

Korhal Senate leader Lennox Craven was unable to control him there. This worried the Confederate Council, as they didn't want to lose control of their most prized colony world. In 2478, with Angus now in his mid-forties, Craven tried a different tactic; disguising neurally resocializedmarines as a corporate death squad and sending them to the Mengsk family summer home when Umojan ambassador Ailin Pasteur and his daughter Juliana had come to visit. However, the attack was inadvertently foiled by Arcturus Mengsk and the Mengsk chief of security, Achton Feld, who had been alerted only because he caught Arcturus trying to sneak into his own house.[1]

Mengsk had planned an underground armed struggle against the Confederacy, and now Ailin Pasteur was prepared to aid him by secretly sending Umojan weapons and other equipment to Mengsk-controlled factories. Arcturus overheard the conversation and disagreed with his father, as he knew these tactics would result in the deaths of people. However, Angus felt that this was a war, and in war, people die.

Angus Mengsk's popularity entitled him to give the Close of Session speech at the Korhal Senate, walking down Senators' Parade alongside Katherine to cheering crowds, going against Feld's previous security arrangements. Upon reaching the Forum he whispered to Craven that he knew the truth behind the "corporate death squad". As part of the speech, he tore down a Confederate flag to raptuous applause. However, he would be personally disappointed that day, as the recently-graduated Arcturus enlisted in the Confederate Marine Corps that morning. Arcturus left without saying goodbye. They failed to connect when Arcturus returned to visit two years later.

The rebellion continued, killing hundreds of Confederate troops in ambushes and explosions with Angus continuing to speak out against the Confederacy. Ailin made regular visits to see Angus in the meantime.[1]

"Not long after I ended my service in the Confederacy, something happened to me; my life's great catastrophe, as I often describe it to myself. You see my father, Angus, was a revolutionary. Back then I didn't share his views, but he caused quite a stir among the people around him. The Confederacy considered him a threat...and they had him assassinated."

By 2489 the Guild Wars had ended, and Angus Mengsk had amassed a millions-strong army when he declared the independence of Korhal.[1] He whipped the Korhalians into a volatile, patriotic frenzy and captured all of the Confederate outposts on Korhal. He garnered the respect and admiration of many other struggling colonies when he declared that the Confederacy no longer held any claim over Korhal. When the Confederates pulled their forces from Korhal and withdrew their fleet from its skies, he and the other leaders of the revolt believed that they had won their independence and celebrated their victory.[2]

The murder of Angus Mengsk prompted his son, Arcturus, to follow a path of vengeance against the Confederacy.[2]Ailin Pasteur would assist Arcturus Mengsk in becoming the next leader of the Rebellion of Korhal, in part because Angus had previously saved his life.[3]

The most important ghost of the trio was Sarah Kerrigan, aka Ghost No. 24, whom Arcturus Mengsk tracked down, originally intending to kill her in revenge for the death of his father. However, after retrieving the then-amnesiac Kerrigan from an experiment involving xenomorphs, he decided she would be more useful as a follower.[3]

Kerrigan learned she had murdered Angus Mengsk from Arcturus Mengsk, who in turn claimed to forgive her. Kerrigan became a trusted and willing member of the Sons of Korhal,[3] but was betrayed by Arcturus at New Gettysburg.[4] Subsequently, Kerrigan pursued vengeance[5][6][7][8] and finally killed Arcturus during the Second Great War.[9]

During his anti-Confederate movement, Mengsk was given a portrait of himself from his constituents to honor his crusade against the Confederacy. The portrait ended up being mounted on the Bucephalus.[10]